The invention further relates to a process for preparing the hydroperoxide according to formula
wherein R1 is a linear or branched hydrocarbon having 1 to 6 carbon atoms and R2 is H or CH3.
These processes are known from EP 0 424 787. EP 0 424 787 describes that an aqueous solution of sulphuric acid is added to a mixture of 2-(3-hydroxypropyl)-1-cyclododecanone and glacial acetic acid. To this mixture hydrogen peroxide (70%) is added, which reacts with 2-(3-hydroxypropyl)-1-cyclododecanone to form a precipitate of a hydroperoxide of 2-(3-hydroxypropyl)-1-cyclododecanone (referred to as DDP-OOH). The precipitate is subsequently filtered, washed with water and then with diluted NaHCO3, after which it is dried.
The resulting dried precipitate was added in portions to a saturated solution of cupric acetate in methanol. Subsequently, FeSO4 was added to this mixture in two equal portions, after which the resulting mixture underwent various steps to obtain a pure product. The product comprises trans-pentadec-11-en-15-olide, trans-pentadec-12-en-15-olide, cis-pentadec-11-en-15-olide, cis-pentadec-12-en-15-olide, and pentadecanolide.
A disadvantage of this process is that the hydroperoxide must be isolated prior to being reacted with the pentadecenolide, rendering the process complex and expensive. Furthermore, the isolated solid hydroperoxide may be unstable and dangerous.
EP 0 889 945 discloses processes for preparing tetradecenolide and 14-methyl tetradecenolide. Because the process described therein is similar to that described in EP 0 424 787, it has the same disadvantages as described above.